Good ending:
Defeat the unknown men and get the Stone of Sealing before you go to the castle and fight with Sol. Defeat the Body of God for the second time in the Royal Tower to view the ending.

Play as Helina from first Lost Kingdoms in Vs:
Defeat the neutral element boss monster in the scared arena (2nd Area) and rather then returning to the beginning continue west to another battle arena. Fight Helina in this arena and defeat her. You must have a skill level of 6 or higher in neutral ability and have defeated the 1st battle arena bosses and the unknown man blocking the arena exit (or if second time or more an extra kendarie knight). This can be done at any time during the game. Defeat her and she appears in the character roster in vs. mode

Play as Katia in Vs. and Download cards from LK:
After you defeat Thalnos in the Scared Battle Arena 2, head north to another arena. Fight Katia and beat her. When you win, the "official" mission will end and it will automatically take you back to the world map. At this point before you can do anything, it will ask you if you want to "Take on Katia's responsibilities". This message is asking you if you want to download your card collection from the original Lost Kingdoms and add it to your current collection (this is the only time that you can do this action for the save file). If you want to, select ok then yes. In any case, save your game and when you load up the file in vs. mode, Katia will appear on the character roster.

Play as Kendarie Warrior In Vs. Mode:
Defeat the Kendarie Card Master Boss (not the lower Kendarie Knights) in the Kendarie Fortress in the first region. Save your game and when you load it again in vs. the Kendarie Warrior becomes available for choosing.

Play as Rashiannu in Vs. Mode:
Beat the Royal Tower Upper Level (This final normal stage for single player mode). Then let the game save the completion settings. When you load up that data in vs. mode, Rashiannu will be available in the character roster.

Play as Thalnos from Lost Kingdoms in Vs:
After you beat Helena and Leod in the Scared Battle Arena 2 (you can only fight Leod here after you beat the game), go to the northern most door in the area and go in. Fight Thalnos and after you beat him save your game. When you load this data in vs. mode, Thalnos will appear on the character roster.

Play as Urbur Cultist in vs. mode:
Defeat one of the cultists that you encounter in battle (most likely, the first one you'll meet is in Ruldo Forest, but any will do), then complete or abort the stage you're on. Save your game and when you load your file in vs. mode, the Urbur Cultist will be available to play (the character is marked as "unknown" on the list).

Duplicate any card
To accomplish this trick, you must have two separate saved games. You can't just save to a different file or memory card. Start a new game, abort the first mission, and save your progress in a separate file.

Now go to the VS mode and load your primary game (the one you want to copy your cards to) for player 1, and your new game for player 2. Wager whatever cards you want to duplicate, then lose to player 2. Load your new game, then save that game in however many slots you want (don't overwrite your primary game!) Go back to VS mode and load your primary game as player 1, and whichever copy of your new game as player 2. Win as player 1, and take back your cards, then go through all the duplicate new games, making wagers of whatever cards you want duplicated. This even works with the very expensive capture card!